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Volume 41, Issue 5
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[in Japanese]1994 Volume 41 Issue 5 Pages 482
Published: May 15, 1994
Released on J-STAGE: May 22, 2009
JOURNAL OPEN ACCESSDownload PDF (78K) -
Shuji Hanada1994 Volume 41 Issue 5 Pages 483-488
Published: May 15, 1994
Released on J-STAGE: May 22, 2009
JOURNAL OPEN ACCESSSeveral kinds of brittle intermetallics have been reported to be ductilized on the basis of fundamental studies on mechanical properties in relation to chemistry of a grain boundary, composition dependence of phase stability, environmental embrittlement, etc. Most of those intermetallics possess fee-, bcc- or hcp-derivative ordered crystal structure and their Peierls stress is relatively low at ambient temperatures. However, many intermetallics having superior properties possess more complicated crystal structure and consequently high Peierls stress. It seems difficult to ductilize these monolithic intermetallics by alloying with a small amount of elements or suppression of environmental embrittlement. A promising process is 'toughening' by distribution of a ductile phase. Refractory intermetallic Nb3Al is shown to have very high strength at elevated temperatures because of high flow stress of an a<100> dislocation consisting of two a/2<100> partial dislocations and a complex stacking fault. Finely distributed Nb solid solution particles in Nb3Al lead to ductility improvement.
Nb3(Al, Sn) superconducting thin wires with a high critical current density(Jc) can be fabricated by heavy deformation and diffusion annealing of Nb/Sn-Al composites prepared by the infiltration process. It is suggested that the interface between Nb3Al and Nb2Al acts as an effective pinning site, thereby increasing Jc.View full abstractDownload PDF (5092K) -
on the Mechanism for the Formation of L12-Al3Ti PhaseMasao Morishita, Kentaro Tanaka, Koichiro Koyama, Masahiko Morinaga, H ...1994 Volume 41 Issue 5 Pages 489-495
Published: May 15, 1994
Released on J-STAGE: December 04, 2009
JOURNAL OPEN ACCESSThe mechanism of the crystal structure transformation of Al3Ti from DO22 to a high symmetry Ll2 by the addition of Cr, Mn or Ni was investigated using the DV-Xα molecular orbital calculation. The calculation suggested that Ti atoms were able to locate at the 2nd neighbor sites of Ti atoms by substituting of Cr. Mn or Ni atoms for a part of the Al atoms which were at the 1st neighbor sites of Ti atoms. This is the reason for the formation of the Al3Ti with the Ll2 crystal structure by the addition of Cr. Nn or Ni.View full abstractDownload PDF (418K) -
Minoru Umemoto, Mamoru Kubosaka, Masamichi Udaka, Kazuhiro Kawasaki, I ...1994 Volume 41 Issue 5 Pages 496-499
Published: May 15, 1994
Released on J-STAGE: December 04, 2009
JOURNAL OPEN ACCESSThe formation of ultrafine intermetallic compound particles in the Al-Cu and Al-Ni systems were examined using a plasma jet method. Pre-mixed elemental powders of Al-Cu and Al-Ni of several tens of pm in diameter were subjected into the plasma jet of Ar-N2 working gas. The ultrafine particles thus formed were examined by X-ray, TEM and EPMA. The main results obtained were as follows; (1) Ultrafine intermetallic compound particles of Al2Cu, AlCu, Al4Cu9 and AlCu3 in the Al-Cu system and Al3Ni, Al3Ni2, AINi and AlNi3 in the Al-Ni system were produced in the present plasma jet method. (2) All the intermetallic compound particles were spherical with the diameter ranging from 1Onm to 100nm. (3) The intermetallic compounds produced were not always with large negative formation energy. Since the cooling rate was relatively fast, the intermetallic compounds which require solid state diffusion at low temperature were not observed. (4) Cu or Ni was richer in the ultrafine particles than that in the source pre-mixed powders. (5) Ultrafine AIN particles were observed when the source pre-mixed powder was Al rich. Such AIN were considered to be produced by the reaction of vapor or liquid Al with the nitrogen in the working gas. AIN was eliminated by using the working gas containing a small amount of H2. (6) The composition of ultrafine particles can be controlled close to that of source powder by reducing the amount of flowing working gas.View full abstractDownload PDF (1502K) -
Kazuhiko Majima, Yoshinori Ozawa, Shigeru Katsuyama, Hiroshi Nagai1994 Volume 41 Issue 5 Pages 500-505
Published: May 15, 1994
Released on J-STAGE: December 04, 2009
JOURNAL OPEN ACCESSThe preparation of Mn-Zn ferrites and Ni-Zn ferrites composed of fine grains has been carried out by hot pressing under various conditions. The results obtained are summarized as follows. α-Fe2O3 was more liable to form in the Mn-Zn ferrrites specimen prepared by the hot pressing than that prepared by the conventional sintering under ordinary pressure due to the remaining O2 in the specimen. Therefore, it was confirmed that the hot pressing process in vacuum was more suitable than in 1%O2 or N2. Mn-Zn ferrites whose grain size is about 2μm was obtained by the process where the specimen was heated to 1248K at the heating rate of 0.028K/s, and isothermal holding under OMPa for 1.8ks and hot pressing under 40MPa in the vacuum of 1.33 × 10-2Pa for the subsequent 1.8ks at the same temperature of 1248K, using coprecipitated Mn-Zn ferritcs powders. Extremely fine grains of about 10-20nm were obtained in both of Mn-Zn ferrites powders and Ni-Zn ferrites powders by MG process, and it was confirmed that using these powders, both specimens of Mn-Zn ferrites and Ni-Zn ferrites prepared by the above-mentioned hot pressing process consist of finer grains than 1μm.View full abstractDownload PDF (4772K) -
Yasuhiro Osafune, Takahiro Uchida, Yosikatsu Nakamura, Yuichi Tanaka1994 Volume 41 Issue 5 Pages 506-509
Published: May 15, 1994
Released on J-STAGE: May 22, 2009
JOURNAL OPEN ACCESSThe influence of the debinding and the sintering condition on the distortion of sintered compact are investigated.
The binder was removed from the compact by two techniques of solvent extraction and thermal evaporation. These processes make it possible to shorten the debinding time than the pure thermal evaporation technique. Relative density of sintered compact in vacuum is higher than in Ar gas. The oxide such as, Al2O3, TiO, TiO2 and TiC are formed on the sintered compact surface, and the depression-distortion is caused at the center of compact. Thicker oxide layer result in larger depression-distortion. It is important to prevent the formation of oxide layer on the compact surface. Embedding the compact in the alumina powder depressed the formation of oxide layer and distortion of sintered compact.View full abstractDownload PDF (4358K) -
Kenji Higashi, Atsumichi Kushibe, Mamoru Mabuchi, Shinji Tanimura1994 Volume 41 Issue 5 Pages 510-513
Published: May 15, 1994
Released on J-STAGE: May 22, 2009
JOURNAL OPEN ACCESSIntroducing the temperature dependence of shear modulus and grain size into the rate equation, the values of n and Q in the powder metallurgically processed TiAl intermetallic were established as 2 and 342 kJ/mol at lower strain rates, and 4 and 334 kJ/mol at higher strain rates, respectively. It is postulated that the lower strain rates may correspond to a superplastic region and stress flow in this superplastic region is controlled by a grain boundary sliding mechanism, but the accommodation process remained unclear because of the unspecified value in true activation energy. Whereas at higher strain rates the n value is high at 4 and the rate controlling deformation in this regime seems to be a diffusion controlled dislocation process.View full abstractDownload PDF (220K) -
Atsushi Nakahira, Hiromu Tamada, Koichi Niihara1994 Volume 41 Issue 5 Pages 514-517
Published: May 15, 1994
Released on J-STAGE: May 22, 2009
JOURNAL OPEN ACCESSCeramic particulate dispersed Ti-Al intermetalic compound composites were successfuly fabricated by hot-pressing the mixtures of Ti and Al (Ti/Al=70/30at%) powders with fine ceramic particulates, SiC and B4C, as the second phases. There were a little reactions between the Ti-Al intermetalic compound and ceramic particulate during the hot-pressing. The microstructure observations showed that both reaction phases and second phases were homogeneously dispersed in the Ti-Al matrix. Their mechanical properties on the hardness and strength were improved by these ceramic dispersions. The relationship between mechanical properties and microstructure was discussed for these ceramic particulate reinforced Ti-Al based composites.View full abstractDownload PDF (998K) -
Yuji Muramatsu, Tsuneo Ohkoshi, Hiroo Suga1994 Volume 41 Issue 5 Pages 518-523
Published: May 15, 1994
Released on J-STAGE: December 04, 2009
JOURNAL OPEN ACCESSIn order to investigate the effect of Cr addition on the sintering of TiAl, We examined the relation between the Cr addition and the sintering behavior and sintered microstructure of TiH3+TiAl3 mixed powders, promising as a starting powder. We examined also the effect of β-phase on the sintering.
The results are as follows: (1) The Cr addition improves slightly the sinterability of the mixed powders, although it has a tendency to promote grain growth, especially in Al-and Cr-rich TiAl a significant grain growth takes place by high temperature sintering over 1620K. (2) The sinterability of the mixed powders is also improved with a decrease of Al content. This is probably due to the β-phase. However, its details are not clarified. (3) The amount of the p-phase increases in increasing Cr content. In relation to sintering temperature, with its rise γ/α2 lamellar structure increases in Al-rich TiAl, and the β-phase increases in Ti-rich TiAl as shown in the Ti-Al-Cr ternary system.View full abstractDownload PDF (5660K) -
Kenzo Fukaura, Nobumitsu Takase, Ryuichi Yamashita, Kanji Ono1994 Volume 41 Issue 5 Pages 524-529
Published: May 15, 1994
Released on J-STAGE: May 22, 2009
JOURNAL OPEN ACCESSNi3Al matrix composites are potential materials for high temperature application because of their marvelous temperature dependence of yield strength. We have tried to make Ni3Al composites reinforced with alumina fibers that have excellent compatibility with Ni3Al matrix by means of powder metallurgy technique. As a result, we feel keenly that ductility of Ni3Al matrix composites at elevated temperature must be made better by alloying element. In this sence, chromium and cerium are added to Ni3Al with boron and tensile properties of these alloys were investigated.View full abstractDownload PDF (3457K) -
Kenzo Fukaura, Nobumitsu Takase, Ryuichi Yamashita, Kanji Ono1994 Volume 41 Issue 5 Pages 530-535
Published: May 15, 1994
Released on J-STAGE: May 22, 2009
JOURNAL OPEN ACCESSThe influence of different mixing methods of elemental powders on microstructures and mechanical properties of Ni-23. 9at%Al-0.5 at% B at elevated temperature was investigated. The main results obtained are summarized as follows;
1)Net mixing processed Ni3Al has much larger grain than dry mixing processed one by a factor of 7. This result suggests that dry mixing provides much more reactive sintering sites than wet mixing.
2)The room temperature yield strength of fine grained Ni3Al is about 720MPa and is roughly twice as strong as that of coarse grained one.
3) Ni3Al processed by both methods reveal a definite positive temperature dependence of hardness and yield strength to a peak temperature of 700K.
4)Yield point elongation can be seen clearly for fine grained Ni3Al. This is associated with the relief of expanded dislocations from Suzuki atmosphere.
5)Fracture mode of dry mixing processed Ni3Al is intergranual ductile at ambient temperatur and it replaces gradually intergranular brittle fracture with increasing temperature. On the other hand, fracture surface of wet processed one is trnsgranular ductile at ambient temperature and it replaces intergranular brittle fracture with increasing test temperature. It is found that transition temperature for wet mixing processed Ni3Al i s about 650K.View full abstractDownload PDF (4277K) -
Keizo Kobayashi, Toshiyuki Nishio, Kenji Miwa1994 Volume 41 Issue 5 Pages 536-539
Published: May 15, 1994
Released on J-STAGE: May 22, 2009
JOURNAL OPEN ACCESSTixAl100-x powders were synthesized by mechanical alloying (MA) of Ti powder and Al powder using a vibrational ball milling in 35kPa Ar. Though MA powders were agglomerated, fine dispersion of Ti and Al elements was performed for 720ksec MA treatment.
Ti-34mass%Al samples, which were prepared by mixing MA powder and Al powder, were hot-pressed at 873K-1173K under 100MPa. The pressing at the melting point of Al enabled 85% deformation of the samples. Furthermore, formation of Ti-Al intermetallic compound was promoted by heating over its melting point. The Ti content in the Ti-Al Intermetallic compound was increased with increasing hot-pressing temperature.View full abstractDownload PDF (3462K) -
Nobushige Hiraishi, Kazutaka Asabe1994 Volume 41 Issue 5 Pages 540-543
Published: May 15, 1994
Released on J-STAGE: May 22, 2009
JOURNAL OPEN ACCESSNi3Si intermetallic compounds have an excellent corrosion resistance in sulphuricacid solution. However, it was difficult to produce these compounds because of poor ductility caused by formation of a very brittle phase. In order to suppress formation of the brittle phase, process conditions involving a mechanical alloying(MA) method have been investigated for the production of Ni3Si intermetallic compounds. First, fine Ni-Si composite powders prepared by the MA method were hot extruded. Then, Ni3Si intermetallic compounds were obtained by a particular heat treatment. Influence of Si contents, MA conditions and heat treatment conditions on the sulphuric-acid corrosion resistance of Ni3Si intermetallic compounds were investigated. As a result, the Ni3Si intermetallic compounds appeared to have a strong correlation between the sulphuric-acid corrosion resistance and the α-phase content. Moreover, an excellent corrosion resistance was obtained when the content of a -phase was less than 5 %. The recommendable manufacturing conditions are as follows: mechanically alloying for 346 ks(B/P=16) using 13.1 mass%Si- 86.9 mass%Ni powders, hot extruding at 1223K and then heat treating for more than 18 ks. Under these conditions Ni3Si intermetallic compounds with an excellent sulphuric-acid corrosion resistance, below 0.3 mm/year, were obtained.View full abstractDownload PDF (2396K) -
Mikio Ito, Kazuhiko Majima, Toshitsugu Takeda, Shigeru Katsuyama, Hiro ...1994 Volume 41 Issue 5 Pages 544-548
Published: May 15, 1994
Released on J-STAGE: May 22, 2009
JOURNAL OPEN ACCESSThe preparation of Sm2Fe17NX permanent magnetic powder whose grain size is finer than the single magnetic domain size of about 300nm has been tried by mechanical grinding(MG) and the subsequent two-step heat treatment; namely the first one is crystallization treatment and the second one is nitriding treatment. The results obtained are summarized as follows:
1)The specimen obtained by MG(as MG'cd specimen) was composed of α-Fe and Sm-Fe amorphous phase, and this MG'cd specimen was found to turn into Sm2Fe17 phase after crystallization and Sm2Fe17NX phase after nitriding.
2)Though the grain coarsening was observed after the two-step heat treatment, the grain size was about 50nm which is much finer than single magnetic domain size of 300nm.
3)The remarkable increment of oxygen content in the specimen was observed by the crystallization treatment. However, such an increment of oxygen content was hardly observed by the nitriding treatment.
4)The maximum cocrcivity of 28 kOc was obtained by the following condition;i.c., MG time:108ks, heat treatment:at 1023K for 1.8ks, nitriding treatment : at 723K for 129.6ks and annealing treatment : at 623K for 7.2ks in N2.View full abstractDownload PDF (2963K) -
Mikio Ito, Kazuhiko Majima, Shigeru Katsuyama, Hiroshi Nagai1994 Volume 41 Issue 5 Pages 549-553
Published: May 15, 1994
Released on J-STAGE: May 22, 2009
JOURNAL OPEN ACCESSThough the process composed of mechanical alloying, crystallization treatment and nitriding treatment has been used to prepare the Sm2Fe17NX permanent magnet powders with high coercivity, the crystallization treatment increases the oxygen content in the specimen.
In this experiment, we tried to prepare the Sm2Fe17NX powders by mechanical grinding(MG) and the nitriding treatment at as low temperature as 623K, where two kinds of powders;i.c., hydrogcnetcd Sm2.5Fe17 powder and non-treated Sm2.5Fe17 powder, were used as the starting materials, and MG was carried out in three kinds of atmosphere ; i.c., in Ar, N2 and NH3 gas.
Though the nitriding was promoted by the existence of hydrogen, the oxidation was also promoted. And it was confirmed that too much hydrogen in the specimen impede nitriding. This phenomenon suggests the existence of the most effective concentration of hydrogen for nitriding. In this work, the nitriding was carried out most effectively on the specimen mechanically ground in NH3, where the nitrogen content after nitriding treatment was about 38000ppm.View full abstractDownload PDF (266K) -
Tetsuji Harada, Seiichiro Takahashi, Toshiro Kuji1994 Volume 41 Issue 5 Pages 554-559
Published: May 15, 1994
Released on J-STAGE: May 22, 2009
JOURNAL OPEN ACCESSMechanical alloying of elemental Nd, Fe and B powders in a composition of Nd2Fe14B was performed in an argon atmosphere by using a high energy ball mill and a conventional ball mill. The structures of mechanically alloyed samples were examined by X-ray diffraction, differential thermal analysis, transmission electron microscopy, scanning electron microscopy and electron probe microanalysis. The results suggested the formation of amorphous Nd2Fe14B materials regardless of the milling apparatus used. In the other hand, the amorphization behaviour and the morphology of the powder particles was deeply dependent on the difference in the accumulated energy given during the milling process.View full abstractDownload PDF (5685K) -
Hiroshi Nagai, Itoshi Maeda, Shigeru Katsuyama, Kazuhiko Majima1994 Volume 41 Issue 5 Pages 560-564
Published: May 15, 1994
Released on J-STAGE: December 04, 2009
JOURNAL OPEN ACCESSThe sintered β-FeSi2 compacts doped with Co and Ni(Fe1-x-yCoxNiySi2, x=0-0.03, y=0-0.04) were prepared by mechanical alloying for 10h and hot-pressing for 30min at 1173K. The effects of Co and Ni doping on the structure and thermoelectric properties of β-FeSi2 have been studied by X-ray diffraction analysis and measurements of electrical resistivity and thermoelectric power. The results obtained are summarized as follows:
1) The electrical resistivity decreased with increasing Co and Ni doping, but the decreasing ratio in resistivity was larger in Co doping than in Ni doping. This is due to the larger solubility of Co than that of Ni in β-FeSi2.
2) All of the sintered β-FeSi2 compacts doped with Co and Ni were n-type semiconductors. The thermoelectric power increased with increasing Co and Ni doping, but over doping caused decreasing of thermoelectric power. Maximum thermoelectric power was obtained by doping with Co:x=0.01 and Ni:y=0.01.
3) Co doping was more effective for increasing power factor than Ni doping, but small amount of Ni doping with Co further increased power factor. Maximum power factor was obtained by simultaneous doping with Co:x=0.03 and Ni:y-0.01.View full abstractDownload PDF (1715K) -
Hiroshi Nagai, Sumio Iida, Shigeru Katsuyama, Kazuhiko Majima1994 Volume 41 Issue 5 Pages 565-569
Published: May 15, 1994
Released on J-STAGE: May 22, 2009
JOURNAL OPEN ACCESSThe thermoelectric properties of β-FeSi2 consolidated by hot pressing of the mechanical grinded (MG) powders were investigated.
Mixture of Fe and Si powders was arc-melted in an argon atmosphere to form a button composed of a -Fe2Si5 and ε-FeSi phases. The botton was grinded in a conventional ball-mill for 20-650 hr. The ball-milled powders were hot pressed at 900°C for 30 min under 25 MPa. X-ray diffraction and EPMA analysis showed that mechanical grinding strongly accelerated the formation of β-FeSi2 during hot pressing and small size particles of ε-phase were dispersed in β-FeSi2 matrix. The amount of ε-phase increased with increasing MG time. The electrical resistivity ρ significantly decreased with increasing MG time, on the other hand the thermoelectric power Q increased with increasing MG time and reached at a maximum at 100 hr MG time, and thereafter decreased with increasing MG time. As the result, the power factor Q2/ρ was at maximum at 250 hr MG time. Thermal conductivity decreased by about 35% with increasing MG time up to 500 hr, but increased again by annealing at 900°C.View full abstractDownload PDF (257K) -
Takeshi Shiono, Kazuyo Miyamoto, Yuka Sugishima, Yasunori Okamoto, Kun ...1994 Volume 41 Issue 5 Pages 573-576
Published: May 15, 1994
Released on J-STAGE: December 04, 2009
JOURNAL OPEN ACCESSForsterite (Mg2SiO4) precursors were synthesized from heterogeneous alkoxide solution including very fine MgO powders and homogeneous alkoxide solution with Mg(NO3)2.6H2O. The precursors from M9O were crystallized to forsterite with drastically exothermic reaction at about 840°C. The precursors from Mg(NO3)2⋅6H2O consisted of Mg(NO3)2⋅6H2O and a little amorphous SiO2. The precursors began to crystallized to forsterite at a lower calcining temperature than those from MgO. However, MgO and enstatitc (MgSiO3) as second phase existed in forsterite powders even at a calcining temperature more than 10O00°C. The forsteritc powders obtained heterogeneous alkoxide solution with MgO showed excellent sinterahility.View full abstractDownload PDF (1369K) -
Masahiro Miyauchi, Tetsuro Nose, Naoki Okumura1994 Volume 41 Issue 5 Pages 577-580
Published: May 15, 1994
Released on J-STAGE: December 04, 2009
JOURNAL OPEN ACCESSA mechanism for crack formation in compacted Mn-Zn ferrites bodies containing PVA during heating process was investigated. The main experimental results are as follows ; (1)The compacted bodies were cracked under the conditions where firing atmosphere changed abruptly from N2 to air at 500°C. (2)Under the same conditions the contraction of the bodies was observed to the extent of 0.6% and the lattice constant of spinel phase determined at room temperature decreased as well. (3)Cracking strain measured by three point bending was less than 0.15%. Based on the results, we consider that cracks were caused by inhomogeneous contraction subjected to atmosphere change, giving rise to surface tensile stress.View full abstractDownload PDF (210K) -
Mok-Soon Kim, Kazuhisa Shibue, Masaki Kumagai, Tsutomu Furuyama1994 Volume 41 Issue 5 Pages 581-587
Published: May 15, 1994
Released on J-STAGE: May 22, 2009
JOURNAL OPEN ACCESSEffect of Al content on the microstructure and room temperature tensile properties has been investigated using a series of titanium aluminides containing 40 to 53mo1%Al (Mn/Al=0.04) produced via a reactive sintering process. A sodium reduced titanium powder is used as a starting elemental titanium powder.
The alloy having 40mol%A1 exhibits a coarse a2 structure in addition to a duplex structure consisted of the lamellar grains and equiaxed γ grains. When Al content ranges from 42 to 50 mol%, the duplex structure is developed, and the volume fraction of equiaxed γ grains increases with increasing Al content. A single phase structure(equiaxed γ)is observed in the alloy containing 53mo1%Al.
Tensile strength rises with increasing Al content up to 43.4mol%Al, after which the strength drops as Al content is increased. Elongation to fracture shows a similar tendency to the strength, although the maximum peak of elongation appears at 45mo1%Al.View full abstractDownload PDF (5372K) -
Mok-Soon Kim, Kazuhisa Shibue, Tsutomu Furuyama, Masaki Kumagai1994 Volume 41 Issue 5 Pages 588-594
Published: May 15, 1994
Released on J-STAGE: December 04, 2009
JOURNAL OPEN ACCESSClose microstructural examination has been made on Ti-(40- 47.3)mol%Al-(1.4- 1.7)mol% Mn intermetallics produced by a reactive sintering using both Na-reduced Ti powders (Na-Ti powders), and Mg-reduced and subsequently hydride-dehydride Ti powders (HDH-Ti powders). The microstructure of compacted mixtures has also been measured.
When HDH-Ti powders are used as a starting Ti powder, both compacted and sintered microstructures have a fine and uniform distribution for all compositions. In contrast, if Na-Ti powders are used as a starting Ti powder, the compacted structure contains a segregated block area of Ti or Al alloys, depending on composition, which results in a coarse α2 structure or a group of y grains in sintered condition. Such inhomogeneous and non-uniform structures are considered to reduce the ductility of sintered materials.
Sintered materials using HDH-Ti powders have a larger grain size and limited micro pore, compared to the materials using Na-Ti powders, due to the reduced chlorine content.View full abstractDownload PDF (7982K) -
Kazuharu Iwasaki, Yoshimi Makino1994 Volume 41 Issue 5 Pages 595-601
Published: May 15, 1994
Released on J-STAGE: May 22, 2009
JOURNAL OPEN ACCESSWe have been investigating the magnetic properties and the microstructure of Co/polymer composite thin films produced by a simultaneous vapor deposition using two evaporation sources of cobalt and polyethylene terephtalate. It was confirmed that the composite thin films having a large perpendicular magnetic anisotropy were deposited, when the incidence angle of the polymer beam was approximately 80 degree. For the composite thin films, the perpendicular magnetic anisotropy energy K1 and the coercivity Hc⊥ measured in the direction normal to the film plane, reached about 5 x105 erg/cc and 1KOe, respectively. The microstructure of the composite thin films consists of columns that Co and CoO fine particles and polymer are mixed. It was observed that the Co fine particles were orderly arranged in a certain direction in columns, and also the <001> axis of hcp-Co was oriented toward the incidence direction of the Co beam Further, the bundles of the columns formed in the direction perpendicular to the incidence plane of the polymer beam were also observed.View full abstractDownload PDF (3793K) -
Young-Taik Choi, Bong-Sun You, Tomio Satoh, Kunio Okimoto1994 Volume 41 Issue 5 Pages 602-607
Published: May 15, 1994
Released on J-STAGE: May 22, 2009
JOURNAL OPEN ACCESSCu-14A1-4(3)Ni-base shape memory alloy is fabricated by centrifugal atomization process. Boron, titanium and zirconium are added to the master alloy, respectively. It is investigated with regard to the effect of these additions on the refinement of microstructure, yields of the powders, powder properties and aging characteristics of the compacts. High yields are obtained in CuAI-NiZr and CuAINiBTi powders. The microstructure of CuA1NiZr powder compact prepared from hot-pressing is refined as compared with those of other compacts. The precipitation time of γ2 phase in the powder compacts prepared by this process is longer than that of the casting having the same chemical composition.View full abstractDownload PDF (5289K) -
Hideto Yoshida, Noboru Miyata, Kazunari Naito, Chitake Yamagishi1994 Volume 41 Issue 5 Pages 608-612
Published: May 15, 1994
Released on J-STAGE: May 22, 2009
JOURNAL OPEN ACCESSInfluence of volume content of carbon fibers (Vf) and elastic modulus of carbon fibers (Ef) on the mechanical properties of Cf/SiC composite was discussed. Fracture toughness and flexural strength of Cf/SiC composites increased with increasing Vf in the range from 40 to 60%. On the other hand, fracture toughness and flexural strength of Cf/SiC composite increased with increasing in the range from 440 to 540 GPa but decreased with Ef in the range between 540 and 640 GPa. The highest flexural strength (1050 MPa at 1450°C) and fracture toughness (25 MPa √m) were obtained by the Cf/SiC composite made of the carbon fiber whose Ef was 540 GPa.View full abstractDownload PDF (1507K) -
Katsuhiro Nishiyama, Keisuke Taguchi, Tsuneo Ohdaira, Masahiko Abe, Ke ...1994 Volume 41 Issue 5 Pages 613-616
Published: May 15, 1994
Released on J-STAGE: May 22, 2009
JOURNAL OPEN ACCESSWe have found the excellent reduction of the coefficient of friction of graphite is generated by boron oxide. The addition of boron oxide was able to reduce the friction coefficient of graphite from 0.4 to 0.1 at 900°C.View full abstractDownload PDF (1266K)
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